I believe the .45 followers went yellow - orange - black with black being the newest. I have all three for my 4516 and 457 and they all work, but I reserve the yellow and orange for range work and only carry with the black. I will buy any used ones I find at a good price ($20-25) as I have a thing about you can't have too many mags and if nothing else I consider them a good investment.

Are you aware that some of the early 4506 magazines had trouble feeding and were recalled by the factory around 1990. They had an orange follower, half moon indentation on the bottom plate and no punch mark at the bottom of the Mag especially on the right side.

You might want to check out some of your local gunshops. A lot of them will have a box of mags that have been traded in or they have just picked up. One near here had a ton of factory 40 cal stainless mags for less than $20. I even found a factory one for my 5906. I think they were all pd trade-ins.

There are at least 4 revisions of the 645/4500 mags. Originals had medal followers and basepads, Orange, Yellow and newest Black. The Yellow followers came in tubes the had a small indent at the top rear of the tube to help hold the rounds back. They required a special follower to clear this indent reason for the "Only use Yellow follower in this mag" warning on the tubes. The Black followers will fit those tubes but came in a tube with square indents on the feedlips themselfs. They hold the top round slightly lower and back and are the latest version. I have had them all and never had a problem with any of them in my guns, but I do have all the newer black follower mags now.